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The influence of ecology on the evolution of reproductive life histories and sociality

English title The influence of ecology on the evolution of reproductive life histories and sociality
Applicant Taborsky Michael
Number 105626
Funding scheme Project funding
Research institution Ethologische Station Hasli Institut für Ökologie und Evolution Universität Bern
Institution of higher education University of Berne - BE
Main discipline Zoology
Start/End 01.01.2005 - 31.12.2007
Approved amount 377'000.00
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All Disciplines (2)

Discipline
Zoology
Ecology

Keywords (3)

evolution of sociality; cooperation; alternative reproductive tactics

Lay Summary (English)

Lead
Lay summary
The first aim of this study was to unravel mechanisms of advanced social behaviour in animals, such as cooperation and reciprocity, by integrating theoretical and empirical approches, observational and experimental methods, as well as ultimate and proximate levels. We used a highly social, cooperatively breeding Lake Tanganyika cichlid fish as a model system. We found that subordinates pay by exhibiting expensive helping behaviour to be allowed to stay in dominant breeders' territories, where they benefit from protection by other group members and from a chance to reproduce or inherit the breeding territory. In exchange, dominant breeders benefit by a reduced workload, a markedly increased reproductive success, and a higher probability of group persistence. We showed experimentally that the interactions and reproductive competition and skew within groups are strongly influenced by sex, size, relatedness and the number of helpers, with important feedback on growth in large male helpers. The latter adjust their growth rate to the size difference to breeder males. Steroid hormones are involved in the regulation of dominance interactions and reproductive competition within groups. Our experiments further revealed that helping effort in this cooperative breeder varies with need (e.g. competition pressure), relative and absolute helper size, and relatedness to male and female breeders. Field experiments revealed that group augmentation and Allee effects are important mechanisms affecting dispersal in these cichlids, whereas habitat saturation and the distribution of food cannot explain their dispersal decisions.Our second aim was to study the ecology and evolution of reproductive competition by comparing fish species with different fertilization mechanisms (substrate brooders, mouth brooders) and social organization (cooperative breeders, colonial or lek breeders, biparental mouth brooders). We made use of the striking diversity of Lake Tanganyika cichlids and focused on five species that covered a wide range of reproductive and social patterns. In substrate brooders using empty snail shells for reproduction we found that the breeding substrate, and not sexual selection is responsible for the greatest sexual size dimorphism in animals with males exceeding the size of females. Alternative reproductive tactics in this species are also highly influenced by the particular breeding substrate, with both, conditional and genetically fixed alternative tactics coexisting within a species. In mouthbrooders, on the other hand, sexual selection seems to mainly influence the mating pattern, with females "demanding" high investment from males into bodily and non-bodily signals. In addition to such pre-mating sexual selection mechanisms, females may induce sperm competition in their mouths, wich constitutes a post-mating sexual selection mechanism that was hitherto unknown in species with external fertilization.This project resulted in 62 publications, including 4 PhD and 6 Master Theses, and in 20 spoken contributions to 7 international conferences in Europe and in the USA. A selection of publications can be downloaded at : http://behav.zoology.unibe.ch/index.php?p=52
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
64396 Mechanisms of conflict and cooperation in the reproduction of vertebrates with advanced social behaviour and alternative mating tactics 01.10.2001 Project funding
118464 Evolutionary mechanisms of cooperation and competition: an integrative approach 01.01.2008 Project funding

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